java - 当使用 Spring Boot Rest Controller 中的其他实体引用映射到 Hibernate 实体的 JSON 时，Jackson InvalidTypeIdException

Question

我正在开发 REST Web 服务，并且我有以下内容:

项目.java

@JsonTypeInfo(include = JsonTypeInfo.As.WRAPPER_OBJECT, use = JsonTypeInfo.Id.NAME)
public class Item implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "item_generator")
    @SequenceGenerator(name="item_generator", sequenceName = "base.item_seq")
    @Column(name = "id")
    private long id;

    @Column(name = "item_name")
    private String itemName;

    @JsonIgnore
    @JsonManagedReference
    @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.PERSIST)
    @JoinTable(
        name="join_category_item",
        joinColumns = @JoinColumn(name="item_id"),
        inverseJoinColumns = @JoinColumn(name="category_id")
    )
    private Category category;
}

类别.java

@JsonTypeInfo(include = JsonTypeInfo.As.WRAPPER_OBJECT, use = JsonTypeInfo.Id.NAME)
public class Category implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "category_generator")
    @SequenceGenerator(name="category_generator", sequenceName = "base.category_seq")
    @Column(name = "id", nullable = false)
    private long id;

    @Column(name = "category_name")
    private String categoryName;

    @JsonBackReference
    @OneToMany(mappedBy = "category")
    @Fetch(FetchMode.JOIN)
    private Collection<Item> items;
{

Controller 类:

@PostMapping(value = "/create",
        consumes = MediaType.APPLICATION_JSON_VALUE,
        produces = MediaType.APPLICATION_JSON_VALUE)
@ResponseBody
public ResponseEntity<Item> createItem(@RequestBody Item item) {
   // some logic here...
}

所以我的问题是，当我尝试使用此 json 从 @Controller 调用 @PostMapping 时:

{
    "Item": {
        "itemName": "Item name",
        "category": {
            "categoryName": "Category Name"
        }
    }
}

我收到以下错误:

"[http-nio-8080-exec-6] WARN org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver - Resolved [org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Could not resolve type id 'categoryName' as a subtype of [simple type, class com.test.Category]: known type ids = [Category] (for POJO property 'category'); nested exception is com.fasterxml.jackson.databind.exc.InvalidTypeIdException: Could not resolve type id 'categoryName' as a subtype of [simple type, class com.test.Category]: known type ids = [Category] (for POJO property 'category') at [Source: (PushbackInputStream); line: 5, column: 4] (through reference chain: com.test.Item["category"])]"

另外，使用

{..., "Category" : {"categoryName": "Category Name"}}

在我的json(大写C)中，不会引发异常，而只是以空类别进入后映射。

提前谢谢您。

Answer 1

删除 @JsonTypeInfo 注释，我认为您尝试使用的 json 结构不需要它们。它们暗示 Item 和 Category 之间存在继承层次结构，但实际上并不存在，Item 仅具有对 Category 的引用。